In the case of the transfer of entropy as, for example, in the use of solar energy or heat sources, such as the combustion of biomass, waste heat or geothermal heat, for example, for a required local supply for pumping power, mechanical drive, electrical energy, for provision of heat, the production of cold, cleaning or separating or the chemical or physical alteration of at least one substance by coupling to a periodically proceeding thermodynamic cycle, the aim is to render as low as possible the necessary outlay on energy carriers or mechanical energy, as well as the design, technological, financial or ecological outlay for
the construction of the entire apparatus, or the operating sequence of the entire method,
the thermal or mechanical energy transport(s) required in this case,
the methods or apparatuses which can be used in this case for the mechanical energy conversion, or
an integrated energy storage mechanism.
The thermodynamic cycles used so far (Stirling engine, steam turbine) are coupled in each case to two heatbaths at a constant temperature. As a result, energy transport can be performed only optically (in conjunction with parabolic mirrors or optical conductors) are via a material flow with a phase transition (heatpipe). Because the aim is an isothermal exchange of heat energy, the thermal energy can be stored only in chemical stores or in PCM devices. As a result, the outlay on concentrating the energy by the collector, on the transport and on a storage which is desirable for many applications becomes all too often excessive. If the aim is direct supply with cold or compressed air, for example, with as little an outlay as possible on apparatus, it is necessary in the case of many known systems to select the path passing via the interface of electrical power.
Object
In the case of a method and/or an apparatus for transferring entropy as in the use of solar energy or heat sources, such as the combustion of biomass, waste heat or geothermal heat, for example, for a required local supply for pumping power, mechanical drive, electrical energy, for provision of heat, the production of cold, cleaning or separating or the chemical or physical alteration of at least, one substance by coupling to a periodically proceeding thermodynamic cycle, whose efficiency is as high as possible, the central object of the invention is to render as low as possible the necessary outlay on energy carriers or mechanical energy, as well as the design, technological, financial or ecological outlay for
the construction of the entire apparatus, or the operating sequence of the entire method,
the thermal or mechanical energy transport(s) required in this case,
the methods or apparatuses which can be used in this case for the mechanical energy conversion, or
an integrated energy storage mechanism.
The above is achieved by means of an apparatus and a method for transferring entropy. At least one working volume filled with a working fluid is largely delimited from other spaces or the surroundings, by at least one valve and at least one pressure housing, optionally without or with a mechanical compression device such as, for example, one or more pistons, liquid pistons or diaphragms, and optionally at least one liquid boundary surface or none, in which:
in each case at least two mutually delimitable structures or structural elements through which working fluid is to flow in a period with a maximum quantity and which have heat transfer surfaces necessarily active for the thermodynamic process, in which in the operating state in each case isothermal surfaces of different temperature which are to be flowed through by the working fluid are formed,
optionally at least one or no element or structural element such as for example, a (foldable) diaphragm, folded, telescopic or resilient sheets, a regenerator structure of changeable shape or a liquid boundary surface, which is arranged between said structures or structural elements in a connecting and largely sealing fashion or is equipped with the action of a regenerator,
or at least one or no displacer piston which can be moved in this working volume,
and the limitation of the working fluid delimit at least one partial volume with a minimum size in a fashion largely free from overlap with a comparable volume and are partly caused by control system elements acting thereon by which, predominantly in those time periods of the periodically proceeding thermodynamic cycle, the ratio of this partial volume to this working volume is either enlarged or reduced during which the size of this working volume is changed in size only to a lesser degree. Depending on the pressure of the working fluid in this working volume, in each case at least one specific valve whose opening and closing times decisively influence the thermodynamic cycle, and which valve can delimit this working volume from at least one external space which is filled up with at least one working means in conjunction with partially differing pressures which are subjected to fluctuations which are only smaller relative to the periodic pressure change in this working volume during these time periods, is predominantly (in the time periods characterized above) held open by the control system or the flow pressure and flowed through. The valve is held closed during other time periods which proceed between these time period and in which the pressure of the working fluid in this working volume either rises or falls through the displacement of the above-named or further components or structural elements by the control system and the variation thereby caused in the mean temperature of the working fluid in this working volume and/or by a variation in the size of this working volume by the mechanical compression device, and the ratio of each partial volume as defined above to this working volume is varied only to a decisively lesser extent, wherein during a time interval which is much longer relative to the period there is either an absorption or output of thermal energy at least of one substance of a continuous or periodically swelling and subsiding mass flow in conjunction with a sliding temperature or with a plurality of temperature levels, and in this working volume at least one working means acts at least partially as a working fluid which traverses the periodic thermodynamic cycle.
The method according to the invention proceeds in an apparatus for transferring entropy, in which at least one working volume filled with a working fluid is largely delimited from other spaces or the surroundings, by at least one valve and at least one pressure housing, optionally without or with a mechanical compression device such as, for example, one or more pistons, liquid pistons or diaphragms, and optionally at least one liquid boundary surface or none, in which:
in each case at least two mutually delimitable structures or structural elements through which working fluid is to flow in a period with a maximum quantity and which have heat transfer surfaces necessarily active for the thermodynamic process, in which in the operating state in each case isothermal surfaces of different temperature which are to be flowed through by the working fluid are formed,
optionally at least one or no element or structural element such as for example, a (foldable) diaphragm, folded, telescopic or resilient sheets, a regenerator structure of changeable shape or a liquid boundary surface, which is arranged between said structures or structural elements in a connecting and largely sealing fashion or is equipped with the action of a regenerator,
or at least one or no displacer piston which can be moved in this working volume,
and the limitation of the working fluid delimit at least one partial volume with a minimum size in a fashion largely free from overlap with a comparable volume and are partly caused by control system elements acting thereon by which, predominantly in those time periods of the periodically proceeding thermodynamic cycle, the ratio of this partial volume to this working volume is either enlarged or reduced during which the size of this working volume is changed in size only to a lesser degree. Depending on the pressure of the working fluid in this working volume, in each case at least one specific valve whose opening and closing times decisively influence the thermodynamic cycle, and which valve can delimit this working volume from at least one external space which is filled up with at least one working means in conjunction with partially differing pressures which are subjected to fluctuations which are only smaller relative to the periodic pressure change in this working volume during these time periods, is predominantly (in the time periods characterized above) held open by the control system or the flow pressure and flowed through. The valve is held closed during other time periods which proceed between these time periods and in which the pressure of the working fluid in this working volume either rises or falls through the displacement of the above-named or further components or structural elements by the control system and the variation thereby caused in the mean temperature of the working fluid in this working volume and/or by a variation in the size of this working volume by the mechanical compression device, and the ratio of each partial volume as defined above to this working volume is varied only to a decisively lesser extent, wherein during a time interval which is much longer relative to the period there is either an absorption or output of thermal energy at least of one substance of a continuous or periodically swelling and subsiding mass flow in conjunction with a sliding temperature or with a plurality of temperature levels, and in this working volume at least one working means acts at least partially as a working fluid which traverses the periodic thermodynamic cycle.
The overall cycle in a working volume can be assigned a plurality of cycles, running in parallel, between in each case two heat reservoirs at constant temperatures, when viewed in the light of acceptable idealization. Each heat reservoir of these cycles can be assigned a partial volume of the working volume, which partial volume is filled with working fluid and defined as above. At least one substance of a continuous or periodically swelling and subsiding mass flow is thus heated or cooled either by absorbing or outputting thermal energy in conjunction with a temperature difference which is small relative to the total temperature change upon contact with the hotter or colder heat reservoir of these cycles, it being possible for the phase or chemical composition to be transformed. In order to use the solar energy, at least one substance of a continuously or periodically swelling and subsiding mass flow is fed thermal energy in conjunction with a sliding temperature or a plurality of temperature levels.
When constructing the integrated collector, the following principles can be very effectively combined on the basis of the temperature change over a large temperature interval:
optical concentration
translucent insulation and
flow through the translucent insulation. The thermal energy can be exchanged very efficiently and cost effectively with the aid of a sensitive accumulator which has a large surface, such as a gravel bulk fill, for example, in conjunction with a through flow of working means. The thermal energy transport can be performed by a movement of a capacitive working means such as air, for example. The pressure change of at least one working means also leaves open the possibility of using a highly problem-free infrastructure to transport the mechanical energy or as an interface for simple further transfer or transformation in order to solve more concrete problems.
These problems have already been taken up in part in Patent DE 3607432 A1. This patent contains a representation of the theoretical principles of a cycle. Citation: column 3, line 45: xe2x80x9cVorliegende Erfindung liefert die Erkenntnisse und praktischen Verfahren, um auch mit einer Wxc3xa4rmezufuhr bei gleitender Temperatur den Carnot-Wirkungsgrad erreichen zu kxc3x6nnenxe2x80x9d [xe2x80x9cThe present invention provides the knowledge and practical experience to be able to achieve the Carnot efficiency even when feeding heat in conjunction with sliding temperature.xe2x80x9d]. The concept for a corresponding heat engine was presented by the applicant of the cited patent in the conference volume of the 6th International Stirling Engine Conference 1993, 26-27-28 May in Eindhoven (Netherlands).
The cited patent does not set forth a physical (phase) and/or chemical change by a transformation of thermal energy over a wide temperature interval, although these problems can be traced back to the same core problem: Because of the variable ratio of the partial pressures, liquefying a portion of the gas mixture generally requires extraction of thermal energy over a temperature interval. Consequently, when evaporating a gas mixture it is necessary to feed thermal energy over a temperature interval or in conjunction with a plurality of temperatures.
Similar statements also hold for a chemical process in which thermal energy is absorbed or output in conjunction with a plurality of temperatures or in a temperature interval.
The preamble and the main claim of the patent cited in excerpts include a limitation to regenerative driven machines or heat engines in the case of which the working volume available to the working fluid is divided into only two periodically variable partial volumes by a rigidly connected structure, which is to be flowed through, of regenerator, cooler and heater as in the known Stirling engines.
Stirling engines with appropriate volumes, temperature differences and speeds such as the machine described in the cited patent are successively described by an isothermal model. Cf.: xe2x80x9cStudie xc3xcber den Stand der Stirling-Maschinen Technikxe2x80x9d [xe2x80x9cStudy on the status of Stirling engine technologyxe2x80x9d]; 1995 in the commission of BMBF; development code: 0326974; page 55 ff Chapter 3.2 ff. The contact made by the working gas with the cylinder walls or the heat exchangers adjoining the partial volumes exhibits no difference, which relates to the application of this model. If this model is applied to the machine described in the cited patent, it must be established that the working gas in the heated partial volume of the working volume expands predominantly isothermally at the temperature of T1 whenever the partial volume cooled at the temperature Tk is smaller, and is predonmiantly isothermally compressed whenever the ratio of the partial volumes is inverse. The working gas in this case traverses a cycle between two heat reservoirs from which or to which thermal energy is extracted or fed at constant temperatures in each case. Except for the cycle of the working gas, with this machine there is no cycle to which it is possible to assign a relevant area in the temperature-entropy diagram or in the pressure-volume diagram. Without violating the second law of thermodynamics, thermal energy, which is fed to the machine at a temperature below T1 can be transported to the cooler only by irreversible phenomena. Similarly, thermal energy which is extracted from a machine above Tk can be transported only be irreversible phenomena and must originate from the heater, since no relevant cycle proceeds in the machine which pumps thermal energy from the temperature level of the coldest partial volume of the working volume filled with gas to the higher temperature level. It is scarcely to be imagined on the basis of this model that the machine described in the cited patent achieves the object set.
In the case of the apparatuses and/or methods not cited, the mechanical work which is fed (consumed) or output (obtained) during a period of the overall cycle for the purpose of compensating the energy balance is for the most part directly converted during the transfer of at least one specified quantity of at least one flowable substance from one storage space into another storage space at a different pressure. Other systems or methods can thereby be integrated simply: Direct use of the pressure change, for example by replacing a mechanically driven compressor, or decoupling the movements in the working volume from the driving shaft of a turbine or a compressor or the like, which turbine/compressor is driven by the pressure difference in the substance flowing (in the closed circuit), or generates this. It is thereby possible, for example, to drive a generator at the usual angular velocity, and to achieve a flow rate of the working fluid of the order of magnitude of 1 m/s against the heat transfer surfaces, and a correspondingly low temperature difference in the case of the heat transfer, and this has a positive effect on the efficiency and reduces the accelerations, occurring at the control system, and the flow losses. This permits a design of large volume in which the pressure in the working volume is in the region of the atmospheric pressure and air is used as working fluid, as a result of which many problems relating to tightness are defused and interesting applications become possible (cf. Examples of Application).
Compared with the abstract formulation of the object as selected above, the cited patent is limited to cooling or heating a heating or cooling medium by thermal contact with heat exchangers of a regenerative driven machine or heat engine. This rules out a reduction in the outlay on design or technology for heat exchangers or regenerators, which is achieved according to the invention when heat is fed into the working volume by virtue of the fact that the heating medium is admitted as a hot gas, for example, into the working volume through valves and output again at a lower temperature through a valve (or valves), as a result of which, moreover, the dead volumes of the working volume can be reduced and, in accordance with experience, this is just as favourable for achieving a high efficiency as is a functional replacement of the relatively small heat transfer surface of the heat exchanger by the very much larger one of the regenerator. Fresh air can flow at atmospheric pressure into the working volume through one of the valves, as a result of which decisive synergy effects can be achieved in some applications. Thus, for example, hot air can be admitted into a working volume and be blown out as cooler air into a space at higher pressure, a portion of the thermal energy released during the cooling of the air having been absorbed by the cooler. Large synergy effects are used in the process when the hot fresh air at atmospheric pressure is heated by exhaust gases of an internal combustion engine, and the cooler air at higher pressure is used for the purpose of supercharging the internal combustion engine (cf. Examples of Application). Cost effective parabolicic fluted mirrors can be employed when solar energy is being used, since the working means can heat air with the aid of the solar irradiation, and therefore no environmental and disposal problems can occur from escaping heating oil, nor is there a need to construct greatly ramified absorber pipeline systems for generating high pressure and steam, and this renders the transport of thermal energy substantially less problematical. Moreover, the heating of the working means over a large temperature interval (for example 200xc2x0 C. to 500xc2x0 C.) is used to achieve a higher final temperature of the working means in conjunction with heating in the absorber of the collector with a relatively low outlay. The principles of optical concentration, translucent insulation and through flow of the translucent insulation can be very effectively combined for this purpose. The co-operation of a nonproblematical accumulator made from cost effective materials even permits the seasonal storage of the insolation over several months, given appropriate dimensioning. A cost effective individual solution, for example the supplying of a remote village or a hospital, is thereby rendered possible.
The following discussion, related to specific applications, makes it easier to understand the formation of the temperature field in the working volume, for example in the case of the use of only one heat exchanger, and the sequence of an overall cycle, together with the problems on which the object is based.